1835.] Decolourizing Combinations of Chlorine. 271 



have been necessary to give up the examination of the pro- 

 perties of this substance if I had not discovered a more 

 economical and productive process. This was by treating 

 red oxide of mercury, suspended in water, with chlorine 

 gas. The action of chlorine upon this compound had been 

 previously examined by Grouvelle, who concluded that the 

 product was an oxichloride of mercury, very little soluble 

 in cold water ; and M. Thenard had observed that the liquid 

 contained in solution, chloride and chlorate of mercury; 

 but, I supposed that their appearance had been preceded by 

 the existence of a chlorate of mercury, as occurred with the 

 silver salts. 



The most favourable conditions for isolating chlorous acid 

 are four : — 



1. The action of chlorine upon a strongly alkaline oxide. 



2. That this oxide may form a chlorite possessed of a 

 certain stability. 



3. That the metallic chloride formed, may, from its inso- 

 lubility, be readily separated from the chlorite. 4. That it 

 may exercise a feeble action upon the chlorous acid, when 

 we attempt to separate the latter by distillation. The red 

 oxide of mercury appeared to possess all these advantages. 

 Accordingly, a greater quantity of concentrated chlorous acid 

 was obtained by the use of this oxide. The most convenient 

 method of producing the acid is to pour into vessels filled 

 with chlorine, the red oxide of mercury, suspended in about 

 twelve times its weight of distilled water. The absorption is 

 so very rapid that the glass vessels are often fractured in 

 consequence of the vacuum formed. If the quantity of 

 oxide is insufficient, the powder deposited is white, and 

 chlorine may be observed in the upper part of the vessel. 

 If the red oxide is added, in excess, the deposit has a red 

 colour, and the chlorine completely disappears. It is pre- 

 ferable to operate with a slight excess of oxide of mercury, 

 in order to avoid a mixture of the chlorous acid with the 

 excess of chlorine. When the absorption of the chlorine is 

 complete, the matter contained in the flask should be thrown 

 on a filter ; the liquid which passes through, when submitted 

 to distillation in a vacuum, furnishes weak chlorous acid, 

 but it may be concentrated by a second operation. 



(To he continued.) 



